Parents know their children cost a fortune to bring up, but it seems the financial commitment lasts well past young adulthood. Not only are mothers and fathers contributing towards the cost of going to university, the first car, the first house and the first wedding, but many are forking out for their children's children too, according to a survey today.

An adult child over 18 costs parents on average £21,540, not counting day-to-day living expenses, says the insurance and investment group LV=, formerly Liverpool Victoria. It is a cumulative rather than annual total, but still a hefty sum for those who might have expected more freedom to spend their money on themselves.

The survey, commissioned from YouGov research, involved nearly 1,200 adults of 40 and over with at least one adult child. Of these, 94% claimed to have contributed financially to the younger generation, while under a third said they had received similar assistance from their parents after they left school. The breakdown of average costs is:

· £5,600 help in buying a home, with nearly a third paying more than £9,000;

· £3,340 towards savings and investments, a fifth donating more than £5000; · £1,700 towards a first car;

· £3,100 towards a wedding, with nearly a fifth paying more than £5,000;

· £2,245 a year towards university costs, totalling £6,735 for a three-year course;

· £1,050 towards travelling.

More than half those questioned said they paid unquantified living expenses as well. LV= says these figures suggest parents spend an estimated £233bn nationally on their adult children.

Although parents over 70 account for only a small part of the sample, 10%, almost half are still helping their children. Many say it is because they feel it is their responsibility to do so, others say it is because they can afford to.

Eight in 10 parents with grandchildren find themselves supporting these too, nearly half helping the youngest generation start savings and investments, and a third paying for some travelling.

London parents are paying most to their adult children, at an average of £26,327, and those in Scotland least, £18,596, helped latterly no doubt by students there not having to pay towards tuition fees.

Nigel Snell, LV='s communications director, said: "More than ever it is true to say that having children means signing up to a lifetime of financial commitment."

Parents feeling the pinch can gain a crumb of comfort from these figures. The cost of helping in adulthood is nothing compared with that for the first 20 years. LV='s last annual survey of the cost of a child suggested each cost a cumulative £186,032 from birth to 21st birthday, not counting private education.